1. Field of the Invention
The present invention relates to a magneto-optical recording apparatus for recording information on a magneto-optical recording medium, and more particularly to a magneto-optical recording apparatus provided with a magnetic head for applying a magnetic field onto a magneto-optical recording medium.
2. Related Background Art
According to the prior art, there are known magneto-optical recording apparatuses which record information by applying a magnetic field onto a magneto-optical recording medium having a magneto-optical recording layer and irradiating it with a light beam. As a recording system for these magneto-optical recording apparatuses, there is a magnetic field modulation system by which information signals are recorded by inverting the orientation of the external magnetic field correspondingly to the information signals to be recorded while irradiating the medium with a laser beam of a desired intensity. Such a magnetic field modulation system is used in, for instance, apparatuses for MiniDisc (MD). In the magnetic field modulation system, a magnetic field is applied from a magnetic head to the optical axis of the light spot of an optical pickup provided opposite the magnetic head with the magneto-optical recording medium between them.
A magneto-optical recording apparatus of the magnetic field modulation system according to the prior art will be described below with reference to FIG. 1 and FIG. 2. FIG. 1 shows a sectional view wherein a magneto-optical disk 8, which is a magneto-optical recording medium, is loaded with a magnetic head 1, and FIG. 2, a sectional view wherein the magnetic head 1 is unloaded. In this prior art apparatus, one end of a load beam 3 is supported by the base 2 of the magnetic head 1 via a first leaf spring 4. To the other end of the load beam 3 is fitted via a second leaf spring 5 a magnetic head slider 7 having a magnetic pole core 6, which is a magnetic field generating unit.
Now, when the magnetic head is loaded as shown in FIG. 1, the magnetic head slider 7 is kept in contact with the magneto-optical disk 8 under a fixed pressure by the springy forces of the first leaf spring 4 and the second leaf spring 5. On the other hand, when the magnetic head 1 is unloaded, the load beam 3 is suppressed in the direction of arrow p by a lifting lever 10 as shown in FIG. 2, and the elastic deformation of the first leaf spring 4 displaces the load beam 3 to shunt the magnetic head slider 7 from the disk surface.
Further, the magnetic head 1 and an optical pickup 12 is linked by a linking member 13. The magnetic head 1 and the optical pickup 12, after being adjusted in position to align the optical axis of the light beam radiated from an object lens 14 provided within the optical pickup 12 and the intensity center of the magnetic field applied by the magnetic pole core 6, are screwed onto the linking member 13.
Incidentally, it is a trend in recent years for the magnetic pole core 6 of the magnetic head 1 to be reduced in inductance by decreasing the sectional area of the magnetic field generating face to be adaptable to high frequency recording in which the magnetic field is inverted at a high frequency of tens of MHz. Therefore, it is important for satisfactory recording and reproduction to align with high accuracy the magnetic field intensity center of this small magnetic pole core 6 and the center of the light spot from the optical pickup 12.
However, the prior art magneto-optical recording apparatus described above requires loading of the magnetic head 1 onto the disk surface over the window portion of a cartridge (not shown) in which the magneto-optical disk 8 is contained, inevitably resulting in a structure in which the load beam 3 in the magnetic head 1 has an inclined portion. For this reason, where the vertical motion of the disk surface due to unevenness of the substrate thickness or surface fluctuation as shown in FIG. 3 is represented by ΔZ, the displacement of the magnetic head slider 7 in a direction parallel to the disk surface at the time by ΔX, and the angles between the disk surface and the load beam when the disk surface is positioned at the top end the bottom end by θ1 and θ2, respectively, there will arise a displacement ΔX in a direction parallel to the magneto-optical disk surface, represented by ΔX=ΔZ×tan [(θ1+θ2)/2] (Formula (1)), will occur. This causes the magnetic pole core 6 of the magnetic head 1 to deviate from the center of the irradiating beam of the optical pickup 12. Since it is necessary to prevent the irradiating beam from being off the magnetic pole core 6 even if the magnetic pole core 6 deviates, the size of the magnetic pole core 6 has to be increased, eventually giving rise to a problem of obstructing high frequency recording.